Method of aerating slurries



106. COMPOSITIONS,

Cross Reference COATING 0H PLASTIC.

- March 26, 1935. A. H. HARRISON METHOD OF AERATING SLURRIES. 7

Filed' July 5, 1932 -'IC I I ARTHUR HUGO HARRISON Patented Mar. 26, 1935l 1. 95. .uNITED' PATENT "OF Pics METHOD or AERATING'SLURRIES v v IArthur Hugo Harrison, Gold Pines, Ontario, Canada, assignor toCarbonated Lime Processes Limited and harden upon hydration, andequall'y'wellto materials, which have not in themselves this settingcapacity but which require some further processing step to bind .theaerated mass into permanent form, such, for example, as lime and clay,which may be hardened by carbonation and burning respectively.

. Various methods of aerating cementitious materials have been proposed,among which may be mentioned the chemical release of a gas in theslurry, whipping air into the slurry, and mixing the premade foamtherein. Some of these methods have been widely used in the productionof porous building materials from plaster of Paris, cement and the like.In view of the greater insulation capacity of cellular materials thesemethods have made it possible to produce greatly improved buildingmaterials.

The object of the present invention is to provide an improved and simplemethod of aeration in making such cellular materials.

The invention will now be described with reference to the accompanyingdrawing which illustrates di 1 n tically the operation of the method andin which,

Figure 1 is a longitudinal sectional view of the apparatus and Figure 2a cross sectional view on line 22 of Figure 1.

It has been found that air can be most successfully incorporated in aslum by suitable agitation, beating or mixing in a closed space and thatthe density of the aerated product can be determined by the pressuremaintained in the closed space during the agitation or As the air iswhipped into the slurry the latter expands to occupy space originallyfilled with the air and when released from the chamber the aeratedslurry expands as determined by the pressure maintained in the chamber.When the pressure in the closed space is varied the density of theaerated slurry and of the hardened or finished product made therefromvaries and adjustment of this pressure provides a ready means ofregulating the density of the finished product.

In the drawing, 1 represents a chamber providing the closed space withinwhich the aeration of the slurry is effected. 2 is a rotatable shaftcarrying radial arms 3 on which are mounted a plurality of bars orpaddles 4, the.

whole constituting the means for uniformly incorporating the air intothe slurry. The shaft 2 is mounted in any suitable bearings and iscaused to rotate at the desired rate by a. motor or any suitable means,not shown. Helically set Application July 5, 1932. Serial No. 620,845

1 Claim. (oral-:12.)

vanes or other means 5of any desiredtype are provided for causing theslurry to travel through the agitating zone at a rate such that therequired amount of air will beincorporated in the slurry during thepassage of the slurry through :5 the agitating zone. The agitating arms4 are preferably shorter than the chamber 1 so as to provide a feedingzone 6 and a discharge zone '7. Slurry is fed into the zone 6 by meansof a pipe or the like 8 discharging near the bottom of the 10 chamber.Air under a predetermined constant pressure is admitted at 9. Theaerated slurry under the influence of the pressure in the chamber isdischarged at 10. A pressure relief valve 1-J,may be provided.

In operation a slurry, comprising a mixture of water and eme laster ofParis lime cla Mme, and conaunn g any suitable BuBBleforming agent, isfed in I the chaber and air elling paddle arms 4 air.is drawn or whippedinto,.eslu where'it s retame in e form' 0 "n es y' the bubble-formingagent. The period of agitation and the rate at 'which the shaft 2travels will influence the amount of air incorporated in the slurry, butin practice these factors are preferably fixed at the most conj venientpoint and the extent of aeration gov- I erned by the pressure maintainedin the chamber. Increase in pressure increases the amount 3 of airoccluded in the slurry and, of course, when i the aerated slurry isdischarged from the cham- X ber the mass expands with the freedom fromsuper-atmospheric pressure.

The following specific examples are given to illustrate the effect ofvariation in the pressure within the chamber. In these cases the shaftof the agitating device was rotated at 270 R. P. M. and the period ofagitation was two minutes.

1. A slurryof Portland cement was aerated 50 as above describe un er 0owing conditions of pressure and the product weighed after being allowedto set for 10 days.

Weight-lbs.

per cu. ft. 55 Agitation at atmospheric pressure Agitation at 30 lbs.pressure 37 Agitation at 50 lbs. pressure 25' 2. A slurry of plaster ofParis aerated under 50 2 days gave the following results.

Weight-lbs. per cu. ft. Agitation at atmospheric pressure.v 68 Agitationat 12 lbs. pressure '82 Agitation at 24 lbs. pressure 51 Agitation at 60lbs. pressure 23 3. A lime slurry aerated as described gave thefollowing results.

Weight-lbs. per cu.1't. Slurry before agitation 77.8

4. A slurry oiLqalgaerated under varying pressures gave the o lowingresults.

Agitation at 50 lbs. pressure 33. 4 Agitation at 83 lbs. pressure 17.5

These examples illustrate the fact that the density of the product maybe maintained at the desired point by control of the air pressureemployed during aeration. The rate at which the agitator revolves andthe time of agitation are mentioned merely as illustrative of what hasbeen done in this respect in practice and are subject to wide variation.

W the character herein us re we u and there are many available. Rosin u.lu r tioned as examples 0 some that may be used alone or in combination.

It will be apparent that aerated slurries of non-cementitious material,such as lime, clay and the like, require further processing to put them2E3 agltated under atmospheric pres- 5 in the form in which they will beused in pracg 'gg 'a' gg'g gggg a t 'ce and such processes are nowavailable in the Agitation at 30 pressure ":jiwrt. The aerated limeslurry may be hardened Agitation at 40 lbs. pressure QB Sa carbona'monthe may by I claim: 7

In the production of cellular building materials the method of aeratinga slurry which comprises admitting slurry containing a bubble-formingagent to a closed space to but partially fill said space, admitting airto fill said space and to provide therein a predetermined pressuregreater than atmospheric, maintaining said predetermined pressureconstant and agitating the slurry to cause at least a portion of saidair to be incorporated therein. I

ARTHUR HUGO HARRISON.

